This invention relates to a method of producing a high density iron-base material. It is more particularly concerned with a powdered metal process for producing an iron-base alloy wherein the desired high density is achieved by liquid phase sintering.
For various reasons, some parts or articles must be made of a material having certain special properties. Often, the most desirable method of producing such parts is by powdered metal methods. For example, parts or articles subjected to certain service conditions are preferably made of an alloy having a high wear resistance. Materials having the required wear resistance are generally extremely difficult or impossible to machine into the desired configuration. Generally, articles made of these alloys are produced in the form of castings and ground to the desired dimensions.
Casting of wear resistant articles may be satisfactory for the production of relatively large parts, but it may be impractical or uneconomical for the production of smaller articles. Therefore, it is desirable to be able to produce such smaller articles by a powdered metal process.
In a powdered metal process of producing these articles, the high density required may be achieved by liquid phase sintering. That is, the compacted article is sintered at a temperature between the solidus and liquidus temperatures of the particular alloy being produced in order to achieve a density of nearly the full theoretical density of the material.
However, some alloys which have very desirable properties such as high wear resistance are substantially eutectic. That is, their solidus and liquidus temperatures coincide or are so nearly equal that it is impractical to control the sintering temperature accurately enough to sinter an article between the two temperatures. Therefore, economical commercial production by powdered metal methods of articles made of substantially eutectic materials has been virtually impossible heretofore.
It is therefore an object of the present invention to provide a method for producing a high density iron-base material by a powdered metal process that overcomes the difficulties encountered heretofore.
According to the present invention, this is accomplished by adding carbon particles to powders of a substantially eutectic alloy, thereby increasing the difference between the solidus and liquidus temperatures and facilitating liquid phase sintering.